Nanostructures formed from semiconducting materials are becoming more prevalent. Many different fabrication methods can be used to produce nanostructures, but they generally have not been able to offer complete control over the pattern and quality of the nanostructures in an affordable and timely manner. One of the most popular methods is reactive ion etching of a patterned substrate. However, this can result in intense damage to the crystal structure and surface morphology. Since many semiconducting applications are very sensitive to defects within the material, it is important to reduce them whenever possible. One method which is becoming increasingly used is metal-assisted chemical etching (MacEtch).
Metal-assisted chemical etching offers a method of etching silicon by patterning a silicon surface with a layer of metal. The metal acts as a catalyst for etching the silicon surface directly beneath it when exposed to an oxidizing agent (e.g., H2O2) and an acid (e.g., HF). Metal assisted chemical etching can produce nanowires of high aspect ratios in silicon (e.g., see U.S. Patent Application Publication 2011/0263119, which is hereby incorporated by reference in its entirety). Since it is a wet etch, MacEtch can easily be done in large quantities for a low price compared to popular dry etch methods that may require a vacuum or plasma. Also, the ability to make structures that are undamaged in any shape capable of being patterned with metal (e.g., gold) has made MacEtch a viable method of silicon nanowire fabrication.
However, MacEtch of other materials, such as III-V materials to produce periodic nanostructures, has hardly been explored and has not been effective in producing high aspect ratio nanostructures.